journeyman
Jeff,
It is not unusual for cast iron pipe to shift outside the foundation, but it seems a little strange that occured inside the house.
Perhaps you have some unstable soil beneath your basement. In any case, it won’t hurt to jack-hammer the area where the suspected problem is.
If the pipe is shifted or damaged in any way, ask your plumber to show you the damage. An easy repair can be made by simply cutting a section of the cast pipe out and reinserting another piece using a double hub fitting which is allowed for repair in most areas that require hard pipe within a building foundation.
As for the cost, it is “considerably less” than replacing an entire house drain.
